Burner utilizing an eddy plate for proper mixing of fuel and air



Sept. 8, 1964 BURNER uni.

w LJQ-LIVINGSTON ETAL 12m; AN EDDY PLATE FOR PROPER MIXING OF FUEL AND AIR Filed Dec. 27, 1961 FURNACE INVENTORS: WILLIAM L. LlVlNGSTON LESTER G. SHARP Q'aaid ATTORNEY United States Patent O Filed Dec. 27, 1961, Ser. No. 162,358 6 Claims. (Cl. 15828) This invention relates to a fuel burner and in particular to a fuel burner which accomplishes a thorough mixing of the combustion air with the fuel, so that a stable flame is established. This is especially significant in an igniter, or pilot burner, the purpose of which is to establish ignition of, or maintain ignition of, the fuel in a main burner.

It is an object of this invention to provide a pilot burner which has a stable flame by providing a thorough mixing of the fuel and air therefore.

It is a further object to provide a burner that is located a distance from the furnace, and is shielded from the heat therefrom, so that the spark plug of the pilot burner is not damaged by overheating.

It is a still further object to provide a burner whereby the size of the flame can be varied, and also the position of the flame can be varied.

Other objects and advantages'of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein FIGURE 1 is a cross-sectional side view of a burner unit; and FIGURE 2 is an enlarged partial view of the apparatus shown in FIGURE 1.

Looking now to the drawings, numeral designates a main burner unit secured or attached to the wall 14 of furnace 12 in any suitable manner. The main burner can use any of a number of difi'erent fuels. As illustrated, oil can be supplied through the centrally located oil gun 16, which is slidable within oil gun guide pipe 18. Gas can be supplied by means of annular passage 20, and pulverized coal by means of annular passage 22. The combustion supporting medium, air, flows through annular passage 24 in a spinning motion, so that it mixes well with whatever fuel is being burned in the main burner 10.

Passage 24 supplies the air for combustion of the main fuel, whether it be oil, gas, or pulverized coal. The spinning motion of the air can be caused by any suitable structure, for example by vanes positioned in the inlet to passage 24. The pulverized coal is caused to spin in the same manner as the air.

In order to initially ignite the main fuel, or to maintain burning thereof, for example when firing at low loads where a minimum amount of fuel is fired and flame stability is thus diflicult, a pilot torch or burner 30 is positioned in the annular space between the oil gun guide pipe and the main burner gas pipe. Air, from a source independent of that supplied the main burner, is furnished to the pilot burner by means of passageway 26. Oil is introduced by means of pipe 31 and nozzle 32. Spark plug 33, when energized, furnishes the spark necessary to ignite the air and fuel of the pilot burner.

A proper and thorough mixing of the fuel and air in the pilot burner is assured by means of eddy plate 28, there being a restricted annular space between the plate 28 and the inner wall of passage 20. Eddy currents are set up in the air as it flows past the edge of cylindrical member 27, which forms part of the eddy plate 28, as best seen in FIGURE 2, causing a small portion of the air to mix with the particles or droplets of oil issuing from tip or nozzle 32, and thus a stable flame exists downstream of eddy plate 28. This flame is not exposed to the high velocity flow of the main portion of the air flowing through ICC passageway 26, which flows past the eddy plate substantially in the form of a hollow cylinder having a radius equal to that of the pipe, and thus there is no possibility that it will be extinguished or blown out by such high velocity air.

Apparatus 46 is a flame indicating device that indicates whether or not a flame is present in the pilot burner. The pressure differential between a point adjacent plate 28 and a point further downstream, adjacent ring 42, is measured by apparatus 46 by means of pressure taps 38 and 40, respectively. The pressure differential between these points is greater when a flame exists than when no flame exists. The operation of this device is more fully explained in US. application Serial No. 771,375 of W. L. Livingston.

Annular ring 42 is supported and maintained in position by means of three equally spaced legs 44, there being passages therebetween. Besides acting to position pressure tap 40, annular ring 42 also acts as a shield to prevent heat radiation from furnace 12 to burner 30, which heat could damage the spark plug 33.

Eddy plate 28 is positioned approximately one and one half feet from the furnace 12 so as to prevent damage to the spark plug due to heat radiation from the furnace. In order to have the pilot flame extend into the furnace a sufiicient distance to properly ignite the fuel and air of the main burner, the fuel issues from nozzle 32 in such a manner that the main portion of such fuel does not start to burn until it is a substantial distance from the eddy plate, for example midway between the eddy plate 28 and annular ring 42. This can be accomplished by having the fuel issue from nozzle 32in a spray having approximately a 60 included angle, as shown in FIG- URE 2. By replacing nozzle 32 with one having a different sized opening, it is possible to have the main portion of the fuel ignited at any point desired downstream of the eddy plate.

It is well known that it is much more difficult to ignite and maintain combustion of pulverized coal than it is for oil or gas. For this reason a larger pilot flame is needed when the main burner fuel is pulverized coal, and thus more fuel and air must be supplied to the pilot burner.

In order to accomplish this varying air supply for the pilot burner and still maintain a constant pressure drop across the eddy plate, thus having the desired eddy currents, a cammed annular ring 34 is fixed to the gas pipe wall. Eddy plate 28 is slidable on oil gun guide pipe 18, and can be moved towards and away from the cammed surface 34 by means of rod 36, thereby varying the size of the restricted annular space between the plate and the cammed surface. Thus when oil or gas are supplied to the main burner, and less fuel and air are being supplied to the pilot burner, plate 28 is moved forward, closer to the cammed surface 34, thereby reducing the size of the annular opening, and maintaining eddy currents of air suflicient to provide a proper mixing thereof with the fuel so that a stable flame exists downstream of the eddy plate.

In operation, air is initially supplied to pipe 26, and the position of the eddy plate is adjusted to obtain the desired pressure drop thereacross. The spark plug 33 is energized, and then fuel is supplied to nozzle 32 through pipe 31, thereby establishing the pilot flame. At this time, the spark plug 33 can be de-energized, and the main burner fuel is introduced, it being ignited by means of the pilot burner flame. The ring 42 helps prevent radiation of heat from the furnace to the spark plug 33, which heat could damage or burn up the electrodes of the plug.

While we have shown and described the preferred em bodiment of the invention it is to be understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

What we claim is:

1. In combination a furnace, a burner unit attached to the furnace, said burner unit comprising: a first pipe to which main fuel is supplied, a second pipe concentric with and surrounding said first pipe, through which air flows, a third pipe concentric with and surrounding said second pipe and adapted to conduct air for supporting combustion of the main, an eddy plate surrounding first pipe and extending radially to a position closely adjacent to the inner wall of said second pipe so as to form a restricted annular passage therebetween, a fourth pipe extending through the annular space between said first and second pipes having an outlet positioned downstream of and adjacent to said eddy plate, through which fuel is supplied, the air flowing past the eddy plate supporting combustion of the fuel supplied through the fourth pipe, and ignition means in the annular space between the first and second pipes positioned downstream of and adjacent to said eddy plate for igniting the fuel flowing through said fourth pipe, whereby the fuel flowing through the fourth pipe forms a pilot for igniting the main fuel fiowing through the first pipe.

2. The combination set forth in claim 1, including flame detecting means positioned in the annular space between said first and second pipes downstream of said eddy plate.

3. The combination set forth in claim 2, including means for adjusting the size of the restricted annular passage between the eddy plate and the inner wall of said second pipe.

4. The combination set forth in claim 3 including means positioned within the second pipe downstream of the eddy plate for protecting the ignition means from radiant heat within the furnace.

5. In combination a furnace, a burner unit attached to the furnace, said burner unit comprising: a first pipe to which main fuel is supplied, a second pipe surrounding said first pipe, through which air flows, a third pipe surrounding said second pipe and adapted to conduct air for supporting combustion of the main fuel, an eddy plate surrounding said first pipe and extending radially to a position closely adjacent to the inner wall of said second pipe so as to form a restricted passage therebetween, a fourth pipe extending through the space between said first and second pipes having an outlet positioned downstream of and adjacent to said eddy plate, through which fuel is supplied, the air flowing past the eddy plate supporting combustion of the fuel supplied through the fourth pipe, and ignition means in the space between the first and second pipes positioned downstream of and adjacent to said eddy plate for igniting the fuel flowing through the fourth pipe, whereby the fuel flowing through the fourth pipe forms a pilot for igniting the main fuel flowing through the first pipe.

6. The combination set forth in claim 5, including means for adjusting the size of the restricted passage between the inner wall of said second pipe and the eddy plate.

References Cited in the file of this patent UNITED STATES PATENTS 1,801,431 Irish Apr. 21, 1931 1,995,099 Herr Mar. 19, 1935 2,284,708 Woolley June 2, 1942 2,325,893 Vollmer Aug. 3, 1943 2,360,548 Conway Oct. 17, 1944 FOREIGN PATENTS 677,697 Great Britain Aug. 20, 1952 

1. IN COMBINATION A FURNACE, A BURNER UNIT ATTACHED TO THE FURNACE, SAID BURNER UNIT COMPRISING: A FIRST PIPE TO WHICH MAIN FUEL IS SUPPLIED, A SECOND PIPE CONCENTRIC WITH AND SURROUNDING SAID FIRST PIPE, THROUGH WHICH AIR FLOWS, A THIRD PIPE CONCENTRIC WITH AND SURROUNDING SAID SECOND PIPE AND ADAPTED TO CONDUCT AIR FOR SUPPORTING COMBUSTION OF THE MAIN, AN EDDY PLATE SURROUNDING FIRST PIPE AND EXTENDING RADIALLY TO A POSITION CLOSELY ADJACENT TO THE INNER WALL OF SAID SECOND PIPE SO AS TO FORM A RESTRICTED ANNULAR PASSAGE THEREBETWEEN, A FOURTH PIPE EXTENDING THROUGH THE ANNULAR SPACE BETWEEN SAID FIRST AND SECOND PIPES HAVING AN OUTLET POSITIONED DOWNSTREAM OF AND ADJACENT TO SAID EDDY PLATE, THROUGH WHICH FUEL IS SUPPLIED, THE AIR FLOWING PAST THE EDDY PLATE SUPPORTING COMBUSTION OF THE FUEL SUPPLIED THROUGH THE FOURTH PIPE, AND IGNITION MEANS IN THE ANNULAR SPACE BETWEEN THE FIRST AND SECOND PIPES POSITIONED DOWNSTREAM OF AND ADJACENT TO SAID EDDY PLATE FOR IGNITING THE FUEL FLOWING THROUGH SAID FOURTH PIPE, WHEREBY THE FUEL FLOWING THROUGH THE FOURTH PIPE FORMS A PILOT FOR IGNITING THE MAIN FUEL FLOWING THROUGH THE FIRST PIPE. 